I have a 75 gal cycled tank. he has 1 green terror, 2 firemouths, a jewel cichlid and a few dither fish giant danios, silver dollars. I know its a bit much for the tank i will be taking out the danios eventually. I have two AC 70s, i do 20-25% water change a week water quality is perfect acording to API test kit and i know my filters are good enough, but my oscar is losing all his black and is turning green. he eats no problem plays swims, shows no signs of sickness, ich, etc. Could this just be him maturing? the orange stripes on his sides are bright as ever its just the black turning to an olive color. he is only about 3 1/2" maybe a lil bigger but not much.. Input please.....

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37 gal mixed African tank(Planted)
75 gal New World cichlid tank-
10 Gal Fry/Hospital tank

Yep! Your Oscar can change colors as it grows. It can get lighter or darker, red or black, etc. when oscars are young, they can instantly change colors depending on their mood.

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36 Gallon Saltwater reef tank
Ocellaris Clown, Scooter Dragonet, sandsifter star, Decorator crab, emerald crab, coralline snails, blue leg hermit crab, and horseshoe crab.
Zooad's and shrooms
40 pounds of Live sand, 20 pounds of LR
Canister filter, 1-unit of chemipure
VHO 2-39W bulbs reef sun/actinic

my baby changed colour all the time....looks wicked!